The present invention relates to devices for testing an automobile. More specifically, the present invention relates to a device for testing an alternator of the type used to charge a battery in an automotive vehicle.
Automotive vehicles include a storage battery for operating electronics in the vehicle and using an electric starter to start the vehicle engine. A battery charging system is coupled to the engine and is powered by the engine when the vehicle is running. The charging system is used to charge the storage battery when the vehicle is operating.
Many attempts have been made to test the battery of the vehicle. One successful technique which has been pioneered by Dr. Keith S. Champlin and Midtronics, Inc. of Burr Ridge, Ill. relates to measuring the conductance of batteries to determine their condition. This technique is described in a number of United States patents, for example, U.S. Patent Nos. U.S. Pat. No. 3,873,911, issued Mar. 25, 1975, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 3,909,708, issued Sep. 30, 1975, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 4,816,768, issued Mar. 28, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE; U.S. Pat. No. 4,825,170, issued Apr. 25, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH AUTOMATIC VOLTAGE SCALING; U.S. Pat. No. 4,881,038, issued Nov. 14, 1989, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH AUTOMATIC VOLTAGE SCALING TO DETERMINE DYNAMIC CONDUCTANCE; U.S. Pat. No. 4,912,416, issued Mar. 27, 1990, to Champlin, entitled ELECTRONIC BATTERY TESTING DEVICE WITH STATE-OF-CHARGE COMPENSATION; U.S. Pat. No. 5,140,269, issued Aug. 18, 1992, to Champlin, entitled ELECTRONIC TESTER FOR ASSESSING BATTERY/CELL CAPACITY; U.S. Pat. No. 5,343,380, issued Aug. 30, 1994, entitled METHOD AND APPARATUS FOR SUPPRESSING TIME VARYING SIGNALS IN BATTERIES UNDERGOING CHARGING OR DISCHARGING; U.S. Pat. No. 5,572,136, issued Nov. 5, 1996, entitled ELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,574,355, issued Nov. 12, 1996, entitled METHOD AND APPARATUS FOR DETECTION AND CONTROL OF THERMAL RUNAWAY IN A BATTERY UNDER CHARGE; U.S. Pat. No. 5,585,728, issued Dec. 17, 1996, entitled ELECTRONIC BATTERY TESTER WITH AUTOMATIC COMPENSATION FOR LOW STATE-OF-CHARGE; U.S. Pat. No. 5,592,093, issued Jan. 7, 1997, entitled ELECTRONIC BATTERY TESTING DEVICE LOOSE TERMINAL CONNECTION DETECTION VIA A COMPARISON CIRCUIT; U.S. Pat. No. 5,598,098, issued Jan. 28, 1997, entitled ELECTRONIC BATTERY TESTER WITH VERY HIGH NOISE IMMUNITY; U.S. Pat. No. 5,757,192, issued May 26, 1998, entitled METHOD AND APPARATUS FOR DETECTING A BAD CELL IN A STORAGE BATTERY; U.S. Pat. No. 5,821,756, issued Oct. 13, 1998, entitled ELECTRONIC BATTERY TESTER WITH TAILORED COMPENSATION FOR LOW STATE-OF-CHARGE; and U.S. Pat. No. 5,831,435, issued Nov. 3, 1998, entitled BATTERY TESTER FOR JIS STANDARD.
With the advent of accurate battery testing, it has become apparent that in some instances the battery in the vehicle may be good, and a problem related to the battery charging system is the cause of a perceived battery failure. A battery charging system in a vehicle generally includes the battery, an alternator, a regulator and an alternator drive belt. In most modern vehicles, the regulator is built into the alternator housing and is referred to as an internal regulator. The role of the charging system is two fold. First, the alternator provides charging current for the battery. This charging current ensures that the battery remains charged while the vehicle is being driven and therefore will have sufficient capacity to subsequently start the engine or run vehicle electronics when the engine is off. Second, the alternator provides an output current for all of the vehicle electrical loads. In general, the alternator output, the battery capacity, the starter draw and the vehicle electrical load requirements are matched to each other for optimal performance. In a properly functioning charging system, the alternator will be capable of providing enough current to drive the vehicle electrical loads while simultaneously charging the battery. Typically, alternators range in size from 60 to 120 amps.
A number of charging system testers have been used to evaluate the performance of the vehicle charging system. These testers generally use an inductive xe2x80x9camp clamp.xe2x80x9d The amp clamp is placed around a cable or wire and inductively couples to current flowing in the cable or wire in the vehicle such that the current can be measured. This measurement can be made without having to disconnect the wire. In such a system, typically the operator determines the rated size of the alternator. Next, the operator connects the amp clamp to the output cable of the alternator and an electrical load such as a carbon pile load tester, is placed across the battery. This is a large resistive load capable of receiving several hundred amps which will force the alternator to provide its maximum output. The maximum output current can then be measured using the amp clamp connection. If the measured output is less than the rated output, the alternator is determined to be malfunctioning. Such a test is cumbersome as the equipment is large and difficult to handle. Further, it is difficult, particularly with compact engines, to reach the alternator output cable. Further, in some cases, the amp clamp may not fit around the output cable. It is also very easy to place the amp clamp around the wrong cable causing a false test.
Another testing technique is described in U.S. Pat. No. 4,207,611, which issued Jun. 10, 1980 and is entitled APPARATUS AND METHOD FOR CALIBRATED TESTING OF A VEHICLE ELECTRICAL SYSTEM. The device described in this reference monitors voltage changes present at the cigarette lighter of an automotive vehicle in order to determine the condition of the alternator by applying internal loads such as head lamps and blowers, while the engine is running.
However, these techniques for testing alternators rely upon monitoring the output from the alternator.
An apparatus for testing an alternator in an automotive vehicle includes a sensor configured to be positioned proximate the alternator which provides a vibration output related to vibrations generated by operation of the alternator. An amplifier coupled to the vibration output is configured to responsively provide an amplified output. A diagnostic system coupled to the amplified output provides a diagnostic output related to condition of the alternator. In another aspect, a temperature sensor is used to perform the diagnosis.